readnum, readstr – device read routines


int readstr(ulong off, char *buf, ulong n, char *str)

int readnum(ulong off, char *buf, ulong n, ulong val, int size)


Readstr and readnum simplify the return of strings and numbers from device read routines, because they deal with any buffering and boundary cases. Several parameters to the read call are often handed on directly to these functions: the file offset, as off; the address of the user’s buffer, as buf; and the number of bytes requested, as n. Both functions return the number of bytes they have stored in buf, and which can often be returned directly from the device read routine.

Readstr satisfies a read by copying data into buf from the NUL-terminated string in str. The data transferred is selected and limited by off, n and the length of str.

Readnum converts the unsigned integer val to a decimal representation in buf. The value is right-justified in a field of size-1 places and is followed by a blank. Size can be the global constant NUMSIZE for 32-bit integers; the largest size allowed is 64 bytes.